Natural Abundance, Single-Scan 13C– 13C-Based Structural Elucidations by Dissolution DNP NMR #DNPNMR
Otikovs, Martins, Gregory L. Olsen, E̅riks Kupče, and Lucio Frydman. “Natural Abundance, Single-Scan 13C– 13C-Based Structural Elucidations by Dissolution DNP NMR.” Journal of the American Chemical Society 141, no. 5 (February 6, 2019): 1857–61.
While 13C-based INADEQUATE experiments offer an attractive alternative for establishing molecular structures, they suffer from low sensitivities arising from the scarcity of spin pairs present at natural abundance. Herein we demonstrate that dissolution dynamic nuclear polarization (dDNP) provides sufficient sensitivity to acquire 1D 13C INADEQUATE spectra in a single scan and at natural abundance. Moreover, if steps are adopted to endow sub-Hertz precision to these measurements, they allow one to measure carbon-carbon J couplings over both one and multiple bonds for each chemical site. As these JCCcouplings are usually sufficiently distinct to enable univocal pairing of the nuclei involved, essentially the same information as in 2D INADEQUATE can be obtained. The feasibility of the method is demonstrated for a range of compounds, including natural products such as α-pinene, menthol and limonene. Features and extensions of this approach are briefly discussed.